The present invention relates to a temperature-compensated zener diode arrangement constructed in the form of a semiconductor integrated circuit which consists of several transistor structures arranged in a common semiconductor body and interconnected by deposited metallizations. The base-emitter pn junctions of the transistor structures are so connected in series with respect to the direction of the total current flowing during operation that part of them are operated in the reverse direction up to the breakdown region as zener diodes, and the remainder in the forward direction as forward-biased diodes.
These temperature-compensated zener diode arrangements have a temperature coefficient which permits them to be used in varactor-tuned radio and television receivers where they generate the temperature-stable and constant bias required to tune the varactors. In this case, the known temperature-compensated zener diode arrangements are operated like a conventional zener diode, i.e., a conventional shunt regulator is formed by means of a series resistor having one end connected to an unregulated dc voltage source.
With the development of the tuners into fully electronic tuners with touch contact operation and remote control capability, the power consumption of the tuning voltage source regulated by means of a conventional temperature-compensated zener diode arrangement has become so large that the zener diode arrangement is traversed by such a high total current as to be operated near the maximum permissible power dissipation, i.e., the temperature of the semiconductor body may be up to 100.degree. C higher than the ambient temperature. The case temperature of the temperature-compensated zener diode arrangement is only slightly lower than the temperature of the semiconductor body.
As a result of this high temperature drop between the semiconductor body and the surroundings, the semiconductor body's temperature may greatly vary despite a constant ambient temperature. The reason is that in the television set further power-dissipating components cause air convection which increases the removal of the heat generated by the temperature-compensated zener diode arrangement. Since, however, this air convection is not of the laminar, but of the turbulent kind, this means that the temperature of the semiconductor body constantly varies with time.
A further change in the temperature of the semiconductor body results from variations in the unregulated voltage, e.g. from line voltage variations. In case of heavy current drain from the shunt regulator, which fact causes the above-mentioned high shunt current in the zener diode arrangement, this may result in this shunt current varying by a factor of 2 to 3 for line voltage variations between +15% and -20%; this, in turn, may lead to a great change in the temperature of the semiconductor body, e.g., to a temperature change from 30.degree. to 100.degree. C.
Since, on the other hand, the known temperature-compensated zener diode arrangements have, of course, a small but not negligible temperature coefficient, such great changes in the temperature of the semiconductor body result in intolerable variations in the stabilized voltage.